Move HTTP from cowboy to livery, and serve HTTP/2 and HTTP/3

[benoitc]

Hornbeam serves HTTP with livery 0.8.0 now, not cowboy. The test suites use livery_client instead of hackney.

What changed

The listener is owned by a supervised hornbeam_listener. hornbeam:info/0 and hornbeam:is_running/0 replace the ranch introspection. hornbeam_handler is a livery handler: WSGI and ASGI responses resolve through livery_resp:stream_deferred/1 in the request process, so body chunks and Python events arrive in one mailbox. WebSocket uses the ws_handler behaviour in the new hornbeam_ws_handler.

Duplicate request headers are kept in the ASGI scope and joined with ", " in the WSGI HTTP_* keys. New max_body option, default infinity.

HTTP/2 and HTTP/3

http_version was documented but nothing read it. It selects the listeners now, default ['HTTP/1.1']:

Value	Result
['HTTP/1.1']	one TCP listener, cleartext or TLS
['HTTP/1.1', 'HTTP/2']	one TLS port, protocol chosen by ALPN
['HTTP/2']	one TLS port, h2 only
plus 'HTTP/3'	a QUIC listener on http3_port, announced with Alt-Svc

HTTP/2 and HTTP/3 only exist over TLS, so they fail at startup with {error, {http_version_requires_ssl, Version}} if ssl is false. It is better than serving HTTP/1.1 without saying anything.

The ALPN listener gives back what cowboy did with start_tls: a client which does not speak h2 gets HTTP/1.1 on the same port instead of a refused handshake.

For HTTP/3 the certificate and the key are converted from the PEM files to the DER form quic wants. Each listener carries its own handler state, so server_scheme and server_port describe the listener which took the request, not the service.

hornbeam:info/0 returns a list of ports per protocol, because one port can serve two protocols:

#{running => true, listeners => #{h1 => [443], h2 => [443], h3 => [443]}}

Request limits

max_request_line_size, max_header_size and max_headers were accepted and documented, but they reached nothing. They reach h1 now, which answers 414 or 431.

One bug fixed

A HEAD response over h2 or h3 killed the handler. The ASGI and WSGI producers only handled {error, closed} from a stream write, and h2/h3 answer {error, invalid_stream_state} when a body is written to a stream which must not carry one. HTTP/1.1 just drops it, so nothing showed before.

Breaking

Routes are livery entries {Method | '_', Pattern, HandlerFun | {Mod, Fun}}, not cowboy {Path, HandlerModule, Opts} tuples. Cowboy handler modules give {error, {invalid_route, _}}.

The three limit keys pass from inert to enforced, so a configuration which set them loosely applies them now. max_header_size maps on the h1 limit for one header value.

hornbeam_wsgi is removed, the build_environ/1,2 path was dead code.

Known limitation

103 Early Hints work on HTTP/1.1 and HTTP/2 but not HTTP/3, which has no interim response in livery yet. The http.response.early_hints ASGI extension is announced accordingly.